When a trial spawner is converted into an ominous trial spawner the mobs spawn with armor if they are able to. If the ominous trial spawner is finished it goes on cooldown and resets after 30 minutes. If you activate this trial spawner again without converting it into an ominous spawner the mobs still spawn with armor which makes it harder.

Steps to reproduce:
1. Go to a trial chamber
2. Activate a trial spawner (zombie, husk, baby zombie, skeleton, bogged, or stray) with the bad omen effect
3. Complete the ominous trial spawner
4. Wait for the cooldown to finish
5. Activate the trial spawner again without the bad omen

Observed results:
Mobs spawn with armor

Expected results:
Mobs do not spawn with armor

https://www.youtube.com/watch?v=Qhbt1Hdaux0